When electrical characteristics of a test object such as a semiconductor package are to be tested, to establish electrical conduction between the test object and a tester for generating a testing signal, there is used a probe unit provided with a plurality of conductive probes and an insulating probe holder that houses and holds the probes corresponding to a wiring pattern of the test object.
Conventionally, as a technology for the probe unit, there is known a technology for fixing a frame-shaped base member, in which metal with high strength such as aluminum or stainless steel is used as a base material and an insulating layer is provided over a substantially entire surface of the base material, to a probe holder for reinforcement (see, e.g., Patent Literature 1). In this technology, an insulating frame-shaped guide member may be screwed to an opening of the base member in order to perform accurate alignment between a semiconductor package and the probe holder.